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Lean running


theminiking

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Hi guys, didn't think I'd be calling on your help so soon!

Only had the car a week and now have a CEL for a multiple cylinder missfire. It's had a bit of a lumpy idle all week and yesterday decided to start cutting out at traffic lights and this morning won't idle at all. Car is a 54 plate UK spec with Vortech supercharger, Nismo exhaust, Kintex cats, Kinetix Plenum, RC550 injectors, Uprev MAF sensor, and remap. Also has a Zeitronix ZT2 wideband AFR which is showing a very lean engine (16 to 17 cruising at motorway speeds), especially at idle when it goes off the scale at AFR 21+ which is a bit concerning.

Does anyone have any ideas what could be causing this extreme leaning? I suspect it's either an air leak after the MAF or a faulty MAF or injector (both only fitted 2 months ago) but I'm just a bit surprised it hasn't thrown up a fault code running so lean?

 

Laurie.

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Definitely sounds like a massive air leak to me. Check all the hoses, gaskets etc.

 

Don't be too concerned about those AFR readings, under light cruise and at idle those numbers are fine. It's under WOT and boost you want to be seeing 12s really.

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Definitely sounds like a massive air leak to me. Check all the hoses, gaskets etc.

 

Don't be too concerned about those AFR readings, under light cruise and at idle those numbers are fine. It's under WOT and boost you want to be seeing 12s really.

 

From what I've read idle AFR should be closer to 14ish, I know it's not dangerous when it's not being driven hard but definitely isn't right! Air leak sounds about right, guess I have an excuse to get to know the 350s engine now then! I did notice one of the intercooler to MAF pipe joints has an extra layer of silicone hose sleeved over the top of it, could be something nasty lurking under there I guess?

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Sussed it! One of the bolts holding down the Kinetix plenum had come loose and the gasket had blown out.

Does anyone know of anywhere that deals in Kinetix spares? I've read that they won't provide a new gasket as it's bonded to the plenum and they want you to return it to the states to get it replaced?!

If not I'll probably be getting some cork gasket and making one.

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